Improve Tekton performance and interface authoring

[elcritch]

Summary

• Make property edits stage only the changed views, preserve live identities and constraints, cache hierarchy/inspector work, and use direct hit lookup.
• Fix stale previews after opening another document, incorrect inspector defaults, decimal parsing, accidental control activation while selecting, setter rollback, and root sizing under constraints.
• Add typed guide/constraint/window/command/asset inspectors, pin-to-parent, grouped undo and deletion, layout diagnostics, sliders and steppers, Open/Save/Save As, explicit interaction mode, preview themes, and a scrolling palette.
• Record findings, benchmark methodology, a rendered screenshot, authoring steps, and remaining work in docs/tekton-review.md.

Scope

This expands resource-document authoring. Attaching to an existing process, controller/outlet/action wiring, menu-tree authoring, and collection editors remain follow-up work documented in the review and PLAN.

Rebased onto main after #114. The dependency manifest now requires FigDraw 0.43.0, whose ownership fix was previously pinned to a deleted branch; this restores clean Atlas installs in release CI.

Validation

On macOS arm64, Nim 2.2.12:

• All four shared runners pass: atlas-run tests, followed by atlas-run tests tests/tnimkit.nim after updating the expected registry kinds for slider/stepper.
• All 41 Tekton tests pass with ASan/UBSan under both ARC and ORC.
• atlas-run tests --compile-only examples/all_compile.nim passes.
• atlas install -tuk --features=kosmo resolves the FigDraw 0.43.0 release.
• Shared test import coverage and git diff --check pass.
• Rendered the editor with Metal and inspected the result; screenshot is included in the review.
• Three alternating benchmark runs measured 300-widget title edits at median 154.158 ms before and 7.743 ms after (~20x faster). Timings include concurrent local build load; factory-count regressions verify the work reduction independently.